Lesson Plan

Volcano Fan Club

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Grade Level:
Sixth Grade-Ninth Grade
Subject:
Climate, Earth Science, Geography, Geology, Landscapes, Volcanoes
Duration:
50 minutes
Group Size:
Up to 36
Setting:
classroom
Keywords:
mount rainier, Mount Rainier National Park, eruption column, lava, lava fountain, Law of Superposition, tephra, volcanic ash, Cascades Volcano Observatory

Overview

Students simulate tephra transport by placing ingredients in front of running fan, and mapping the resultant layers. This lesson plan is part of the "Living with a Volcano in Your Backyard" curriculum, created through a partnership between Mount Rainier National Park and the US Geological Survey Cascades Volcano Observatory.

Objective(s)

Students will:

  • Recognize how wind influences the dispersion pattern of tephra.
  • Understand the energy transformations that occur during tephra fall.
  • Recognize how volcano researchers assess the area of tephra fall.

Background

What is tephra?
The term tephra refers to fragments of volcanic rock and lava of all sizes that are blasted into the atmosphere by explosions or carried upward in eruption columns or lava fountains. Large pieces of tephra fall to the ground first. Smaller pieces stay aloft for longer periods of time which allows the wind to blow tiny particles to a great distance from the volcano.

Volcanic ash refers to the tiniest pieces of tephra, smaller than 2 mm (0.1 inch) in diameter, which is a bit larger than the size of a pinhead. It is formed during explosive eruptions by the shattering of magma. Volcanic ash is not a product of combustion, such as ash formed by the burning of paper or wood. It is hard and very abrasive, mildly corrosive, and is electrically conductive, especially when wet.

Building tephra deposits
Once ejected into the air, the wind carries tephra particles. How far a tephra particle travels depends upon wind speed and size of the eruption. Coarse and heavy particles fall on or near the volcano; fine-grained, lightweight particles travel farther. The resulting tephra layer on the ground is progressively thinner and finer-grained with increasing distance downwind from the volcano. Viewed on a map, the plume trace and tephra layers are generally in the shape of an elongated oval. At high wind speeds the tephra layer is long and narrow. At lower wind speeds the tephra layer is shorter and wider. When there is no wind, the tephra deposit may be circular around the vent.

During successive eruptions tephra might fall in a similar pattern, overlapping or covering completely the older layer. Geologists establish the relative ages of layers by looking at the order in which the layers were deposited. As stated by the Law of Superposition, layers that are younger will be deposited on top of layers that are older. 

Meteorological records show that at the Cascade Range volcanoes, the wind blows most often from west to east. This trend in wind direction during ancient eruptions is revealed in multiple tephra layers that are thickest on the east side of the Cascade Range.

The extensions in this activity provide opportunities for students to determine the path of volcanic ash after its eruption from a Cascade Range volcano.

Four clues to reading a tephra deposit
Geologists reply on four principal lines of evidence when they interpret tephra layers and identify their volcano of origin:

  1. Tephra layers are thickest near and on the source volcano.
  2. Coarse tephra falls to the ground before finer-grained tephra.
  3. Younger layers overlie older layers.
  4. A unique chemical signature exists at many volcanoes that allow researchers to match tephra with its source volcano. This fourth clue holds great importance to geologists, though it is not addressed in this activity.

Once your students understand these concepts and conduct the activity, they can be part of the volcano fan club!

 

Materials

Instructions and worksheets for students and teachers for use in the Volcano Fan Club lesson plan.

Procedure

Assessment

For assessment, instruct students to show results of their experiment in an illustration, or to diagram or graph the class results on a whiteboard. Review the student page results and look for evidence of student recognition that coarse materials fall first, followed by fine-grained material. Students should demonstrate ability to measure the area of the concentrated tephra; graph the data and interpret it. Instruct students to draw stylized diagrams of any tephra deposit formed by far-traveled winds, and by an eruption with no winds. Assess application to real-world situations by assigning interpretation of an additional ready-to-interpret data set of your choosing, and by asking questions about how this pattern of distribution might affect all regions of your state.

Park Connections

In the event of an eruption at Mount Rainier this activity displays the impact of tephra on surrounding areas.

Extensions

Simulate effects of ash fall on a map landscape.
Simulate effects of ash fall on the region around a volcano. Obtain a large paper map that shows a volcano and surrounding landscape, including towns and cities, roads, airports, and other features. Place children's toy plastic animals, cars, trucks, airplanes, school buses, and emergency vehicles on the map surface. Set up a fan on the volcano to create wind. Simulate volcanic ash, either with the use of real volcanic ash, or fine silt or clay, cocoa powder, or flour. Students use a spoon to ladle the "ash" in front of the wind created by the fan. Students observe and discuss which areas are ash covered, and effects on animals, transportation, and communities. Research websites that describe the effects of volcanic ash. 

Determine the path of volcanic ash using data at the American Meteorological Society's Data Streme website.
This extension requires students to possess some understanding about meteorological maps and atmospheric pressure and its control over wind direction and speed. Students estimate the travel direction and speed of an ash plume at a Cascade Range volcano. Instruct students to visit the American Meteorological Society's Data Streme web pages. At the website, students observe the wind speed and direction in the upper air above a Cascade Range volcano of their choice. They note the pressure levels for 850mb, 700mb, and 500mb, then assume that an eruption hurls volcanic ash to an altitude of six kilometers (~20,000 feet). Students make predictions about where the ash will travel to in 9 hours.

Additional Resources

Frances, P., Oppenheimer, P., 2004, Volcanoes: Oxford University Press, 521 p.

 

Kenedi, C.A., Brantley, S.R., Hendley, II, J.W., Stauffer, P.H., 2000, volcanic ash fall— a hard rain of abrasive particles: U.S. Geological Survey Fact Sheet 027-00, 2p..

 

Myers, B., Brantley, S.R., Stauffer, P.H., and Hendley, J.W., 1997, What are volcano hazards? (revised March, 2008): U.S. Geological Survey Fact Sheet 002-97, 2p.